design of steel structures which inculudes plastic analysis , of a steel

design of steel structures

1. UNIT-I PLASTIC ANALYSIS

2. SHAPE FACTOR Ze is the Elastic Section Modulus Zp is the Plastic Section Modulus Ze is used to determine the maximum bending moment up to the point where the extreme fiber has yielded elastically. All other fibers will be below their elastic yield stress. Zp is used to determine the maximum bending moment at the the point where all fibers have yielded elastically and the entire section is behaving plastically. This is the point when the so called plastic hinge has developed. Shape factor is just the ratio of these two parameters, it has no physical meaning, it is just useful in computation.

3. SIGNIFICANCE OF SHAPE FACTOR S hape factor signifies how much extra moment a member can take after attaining the first yield ( i.e , attaining yield strength by the extreme fibers ). It is a geometric property not a material property. For example shape factor ‘S’ for rectangular section is 1.5,which means 50 % extra moment a member can take after attaining first yield . Shape Factor is a dimensionless number that characterizes the efficiency of the shape, regardless of its scale, for a given mode of loading, e.g. bending, torsion, twisting, etc. We all know that type of material governs the strength of structural member. Similarly , the cross-sectional shape of a member is responsible to enhance the load bearing capacity of section.